The present invention relates to a blood-viscosity reducing agent which reduces the viscosity of whole blood.
Natto has been Japanese traditional fermented food taken from the 1600s to the present for a long period of time and is excellent as food which allows Japanese to ingest soy protein efficiently. For example, natto has a higher digestibility than soy beans. This is because the protein, fat, starch, and the like as the main ingredients of soy beans are decomposed into an amino acid, fatty acid, and glucose by Bacillus subtilis natto, and digestibility upon ingestion is enhanced.
Most of the vitamin B family contained in natto smoothes physical functions and shortens fatigue recovery. Natto contains a large amount of vitamin B2 and is expected for recovery of asthenopia. The content of vitamin K in natto is the highest among the foodstuffs. Natto can be expected to improve blood calcium metabolism, e.g., to prevent osteoporosis and improve the blood clotting ability.
In recent years, a variety of functions of natto have been clarified, and natto's effects have received a great deal of attention as health food. The consumption of natto has been increasing. Particularly, the natto-containing enzyme called Nattokinase is effective as fibrinolytic and thrombolytic agents, as the production methods, physicochemical nature, and biochemical nature are disclosed in Japanese Patent Laid-Open Nos. 61-162184 (reference 1), 3-168082 (reference 2), and 6-153977 (reference 3).
Nattokinase has received a great deal of attention as a thrombolytic agent or thrombogenesis inhibitor, as described in Japanese Patent Laid-Open Nos. 1-180834 (reference 4) and 8-208512 (reference 5). These references disclose techniques associated with safe, easily accessible agents containing Nattokinase as the active ingredient in place of agents, i.e., a thrombolytic agent and platelet aggregation inhibitor such as urokinase, streptokinase, and a tissue plasminogen activator, which are currently used for thrombus in the clinical field.
Japanese Patent Laid-Open No. 2001-352929 (reference 6) discloses natto's processed food produced in the following manner. In a state wherein flavour unique to fermented natto is absent, the active ingredient unique to natto is extracted from a dialyzed medium in which soy protein powder purified from soy beans is cultured with Bacillus subtilis natto. According to the proposal of reference 6, the use of this processed food allows to delay blood clotting time and suppress thrombogenesis in addition to the thrombolytic effect using Nattokinase.
As described above, the product derived from natto has various effects such as the delay of blood clotting time and suppression of thrombogenesis in addition to the thrombolytic effect. The present inventors found a new function other than the above effects in the natto's processed food disclosed in reference 6.